This summer I purchased two Ubiquiti Nanostation M2 wireless devises with the intent of beaming wireless internet from my house to my bin site that is about 8,000' away. I didn't get it put up on time and finally started working on it today. The antenna at home is on my roof about 30 feet in the air and it is clear line of site to the bins. I do not have the bin antenna up yet but decided to drive over with my laptop and see if it works. To my amazement I had a very usable signal at the bins! Ubiquiti makes some pretty bold claims for their distances and I was skepitical. I recall reading about 15km connections and suspect that if the conditions were correct it may be possible. I may try with two devices pointing towards each other at a pivot I have about 4 miles away.

Which one of their devices are you using? I have a simular task in mind.